Chrome-iron sheet or article and process of making same



May a, 1923. O 1,454,464

F. M. BECKET ET- AL CHROME IRON SHEET OR ARTICLE AND PROCESS OF MAKING SAME Filed March 5, 1922 Patented May 8,

PATENT OFFICE.

FREDERICK M. BECKET, OF NEW YORK,-AND CHARLES E. MGQUIGG, F FLUSHING, NEW YORK, ASSIGNORS TO ELECTRO METALLURGICAL 00., A CORPORATION OF WEST VIRGINIA, p

CHROME-IRON SHEET 0R ARTICLE AND PROCESS OF MAKING SAME.

Application filed March}, 1922. Serial No. 540,885.

To all. whom it may comm.

.Be it known that we, FREDERICK M. BEOKET and CHARLES E. MoQUIoG,citizens of the United States of America, residing at 5 565 Park Avenue, New York, and 356 Madison Ave, Flushing, L. I., in the counties of New York and Queens and State of New York, have invented certain new and useful Improvements in Chrome-Iron Sheets or Articles and Processes of Making Same, of which the following is a specification.

This invention relates to'ductile alloys of iron and chromium, and especially to such alloys in sheet form min the form of articles embodying the sheet form of the alloy;

and comprises a process whereby such physical properties may be imparted to the alloy .as will-enable its conversion into sheets or sheet-metal articles of relatively high ductility. The invention comprises also the relatively ductile sheetor other article which I may result from the practice of the said :process, as well as the process involved in the manufacture of the said ductile sheet.

- alloys comprising chromium and iron, asso ciated with a small proportion or carbon 3 (say not in excess of one percent) may be worked into sheet or other forms provided the chromium content does not exceed a definite maximum which lies in the neighborhood of 16%. Such alloys are non-tarnishing in air at ordinary or somewhat higher temperatures, and have found many applications in the arts. Such alloys are however incapable of withstanding the oxidizing action of air at extremely high temperatures, as from 1000 to 1100 C. Alloys containing substantially higher percentages of chromium than the above, say approximately 20 per cent or upward, are substantially non-oxidizable in air at these high temperature ranges, as already disclosed in a prior. Patent No. 1,245,552 patented Nov. 6, 1917, to F. M. Becket; but such-alloys have never to our knowledge been successfully rolled-into sheet of commercial grade and quality; although they have been successfully forged into a great variety of articles. In this connection it should be clearly understood that analloy which is capable of being rolled into sheet can also, as a rule, be hot-pressed or drawn at least into relaalloys It is now well understood in this art that tively shallow forms; and conversely an alrolled: but many alloys can be forged or swaged, although they can neither be rolled nor drawn. For example in the prior patent t0 Becket, above mentioned, referring to ciatedwith say 1.5-3.0% of carbon it is stated: I

4 'Alloys within the" limits above specified possess a, strongly marked fibrous structure. They can be forged and machined, although with difi'iculty as compared with ordinary steel. They can'be annealed and also tempered, and in general are responsive-to heat treatment, although to a materially less degree than ordinary high-carbon steels.

containing 20-35 of chromium asso-.

It is obvious that'great commercial and technical advantages would follow if ironchromium alloys lying within that we will ,term the non-oxidizable range, meaning thereby substantially non-oxidizable in air at all temperatures up to 1000 or 1100 (3., could be transformed into non-brittle sheets and into the numerous commercial articles which might with advantage include or embody the metal in sheet form: and it,.is av primary object of the present invention to provide. a process by which this result can be accomplished in a practical and commer-' ,cial manner. In the practice of our-process in its pre-' ferred embodiment we prepare a non-oxidizing alloy containing upward of 20 per cent of chromium, associated with some carbon, the balance being principally iron. Relativtlaly small proportions of other. metals, suc like may of course be present, provided they are not in sufficient proportion to interfere with those properties'of the alloy' which are essential to our present purposes. Ve prefer a carbon-content below 0.5 and in general, the lower the carbon content the more readily and cheaply. the alloy is rolled or drawn. 'But our invention is not restricted to such low carbon ranges, as we have sucas manganese, silicon, copper or the cessfully rolled 'allo scontaining in excess of 1 per cent of car n. High carbon content is however usually regarded as undesirable, not only on account of the increased difficulty and expense of rolling as mentioned above, but because thehigher carbon diifer sharply relativel poor welding properties of the a-l-' 10y, wit the attendant risk of/breaking down the nherently weak .la'rge crystals before-the refining has taken place.

We have discovered that'in order to impartto the alloy such ductility as will permit us to make a finishedsheet of'satisfactory \ essential first that the sheet should be cooled on the quali t range 600 400 a i are relatively t in;

' aria-teena e from a temperature not lower than" about 600]CL'and' referablyBOO or 900 (1.; and

se cond'that the cooling from about 600' 'to about400 C. should be rapid. The rate of coolingflbelow about i00 C. or above about 600 C. seems-to be without substantial effect of. the alloy. If however the sheet is permitted to cool slowly through the C; it is liable to become so embrittled as to be'non-usable' for most com mercial purposes. It will ofcourse be understood that the upper'and lower limits of this embrittling temperature range are only approximately expressed ferent alloy compositions do not act identically in this respect;- but good results can be assured by rapid cooling through 'the range specifi d. Sufficien'tly rapid cooling can be secured in the case of thin sheetsby'au air blast; butwith thicker sheets the'bestpractice involves quenching from a temperature not less than 600 C.

There are two principal ways in which ductile sheets maybe prepared in accordance with our process. way, the rolling with or without reheating between passes is carried through in such manner that thefinishing temperature will lie above 600 C., in which case the sheets can be quickly ,cooled'through the embrittling range of 600 400 (I, with resulting direct production 'of commercially ductile sheets- This ishow'ever often difficult of accomplishment; articularly when the sheets and linsuch case substantially' the same result cam-be attained by reheating thefinished sheets to a point above 60'0" C."'-and. referably tdor above800", C.

temperature --is be .tween 800 and 1000- G'. The higher-thepreferred merci al purposescarbon or chromium content ductility and physical properties, it isabove, since dif-.

According to the first W Y, H For the' best'. resultsthetotal'tiniediiring which the metal" is passin through the range from 6OO"-et00f Cisho uld not'muc'h exceed-brie minute; and is' prefe'rably asmuch less than this as is practicable under the particular circumstances; q v J 1 By application .of the. above principles we have been able to prepare chromeirontsheets of a degree of ductility adequate for; com:

from a-wide range of inoxidizable alloys, varying from a minimum chromium content-approximating 20%, to

a maximum of about 60% and it is probable that the principles are applicable even above this latter figure. The property of ductil-v ity as, the term is used in this. specification may' gbe indicated or measured in various ways, as for example by the so-called bend test or, and preferably, by the Erichse n value. According to this last-mentionedtest a rounded pointof standard radius ofcurvm ture is pressed into the surface, of'atmarginally supported sheet of the'metal'to-be tested to a depth atfwhich the, initial fr'acture' occurs, the depth of 'penetrationex,--

in millimeters being the Erichsen pressed" value. A' typical chrome-iron sheet, prepared in accordance with this invention from alloys within the non-oxidi'zable' range,

will give an Erichsen value not less than 5, and upto? or higher, for a 20 gauge sheet.

'For .agiven alloy composition and thick nessof sheet, providing in all'cases that the metal has been properlycarried throughthc embrittlingrange of about 600400 Erichsen value appears. to depend directly upon the temperature from which the sheet has been cooled. This relation is graphically shown in the; accompanying drawing, in which the figure is a curve expressing in millimeters the Erichsen values of a No. 20 gauge sheet (.020 inch in thickness) rolled o, as, Y

from an alloy of the following composition:

Percent. Chromium 28.50 Carbon; i- 0.83; Silicon 0.79 Manganese 0.28

the balance substantially all iron; the sheet being cooled from various temperatures as indicated-on the drawing. As will ,be noted,

in this particular case the values rise from aminimum of 2 in the sheet cooledfrom a temperature lying within the embrittling rangeof 400 45005 .to a maximum'of' 7 at our preferred rollinglor reheatinglrange of S00-10009 C.;'and again tend to fall as this temperature is exceeded." ltHwill b'e understood bythose familiar. with-this art,

that'a specific Erichsen number is valid only for a definite thi'cknessof sheet;- but for any given metal i'the" rallies "for varying\ sheet' thickness" follow 'a' known type" of curve, so: that the, corresponding yalue's' tor 'othersheeti thiclm'e'ss'es can as a rule be approximated with suflicient accuracy for commercial purposes. F or this reason the Erichsen value for a given sheet thickness will serve as an index of the ,quality of ductility in the metal. So far as we are aware, we are the first to prepare chrome iron alloys within the non-oxidizable range, that is to say containing more than about 20% of chromium,- in the form of non-brittle sheets; and We regard such sheets, or articles made from or embodying the same, as a part of our invention. The term sheet is employed herein in its broad sense, to include those heavier products which are sometimes designated in the trade as plate.

It has heretofore been believed that the workability of iron-chromium alloys decreases quite regularly with increasing chromium content. Our investigations have disclosed however that such is by no means the case, and that at least over a very considerable range of carbon content, alloys containing upward of about 40% of chromium are decidedly more easily worked than are alloys of similar carbon content but contain ing around 3035% of chromium. As an example of this we have been able readily to roll into a commercial grade of sheet alloys containingin addition to iron:

Chromium 52. 38 52. 20 Carbon 2. l8 1. 4:0 Silicon 1.00 0. 75 Manganese 1.36 0. 66

Such alloys not only possess the characteristic of resistance to oxidation at high temperature ranges, but possess qualities of resistance to many chemical reagents which fit them particularly for such specific uses as dental spatulas, surgical instruments and the like.

lVe claim:

1. Process of making chrome-iron sheets or articles of. relatively high ductility, comprising mechanically reducing the metal to sheet by rolling, drawing or equivalent steps; and subsequently rapidly cooling the heated sheet through the temperature range 600400 C.

2. Process according to claim 1 in which the rolled or drawn sheet is reheated, and then rapidly cooled through the temperature range 600'400 C.

3. A non-brittle sheet or article havin the characteristics and structure of rolled or drawn iron-chromium alloy; presenting surfaces substantially non-oxidizable in air up to at least 1000 (3.; and containing upward of 20% chromium, the balance principall iron.

4. A non-brittle sheet or article having the characteristics and structure of rolled or drawn iron-chromium alloy; presenting surfaces substantially non-oxidizable in air up to at least 1000 C'.; and containing upward of 40% chromium, the balance principally iron. v

5. A sheet or article having the character istics' of rolled or drawn iron-chromium alloy; presenting surfaces substantially nonoxidizable in air up to at least 1000 0.; and containing upward of 20% chromium, the balance principally iron; said article havingsubstantially higher ductility as measured by the Erichsen value than a non-heattreated sheet of the same thickness and composition.

6. A sheet or article having the characteristics and structure of rolled or drawn ironchromium alloy; presenting surfaces substantially non-oxidizable in air up' to at east 1000 (3.; and containing upward of 20% chromium, the balance principally iron;

said article having an Erichsen value of not less than five millimeters in a thickness corresponding. to that of .a 20 gauge sheet.

7. A rollediron-chromium alloy containing upward of 40% chromium, and upward of 1.5% carbon, iron.

8. A rolled iron-chromium alloy containing upward of. 40% chromium.

the balance principally 9. A non-brittle heat-treated sheet or article having the characteristics and structure of rolled or drawn iron-chromium alloy, and containing upward of 40% chromium, the balance principally iron.

10. Process of heat-treating chrome-iron alloys to impart ductility thereto, comprising rapidly cooling the heated alloy through the temperature range 600400 C.

In testimony whereof, we aifix our signatures.

FREDERICK M.-BECKET. CHARLES E. MOQUIGG. 

